The present invention relates to battery driven electric vehicle control system. More particularly, this invention provides a highly reliable electric vehicle control system driven by a simple arrangement.
Battery driven electric vehicle control systems have been described in the past, including the methods in the Japanese Laid-Open Patents 3-251002 and 2-133005. The former method in the Japanese Laid-Open Patent 3-251002 uses a simple drive system to drive a vehicle in which a single inverter controls a single motor. The latter method in the japanese Laid-Open Patent 2-133005 provides an optimized drive force for each of a plurality of motors to make the vehicle operate highly efficiently, thereby increasing its running distance per charge.
Methods for driving an ac motor with a plurality of power converters are also known, including, for example, the methods disclosed in the Japanese Laid-Open Patents 63-323589, 63-305792. These methods for driving a plurality of windings of an ac motor, with respective power converters, are suitable for high capacity.
Each of these prior art devices, however, suffers from at least one particular disadvantage. In the first prior art control mentioned above, if there is a failure in the power converter for driving the motor, the motor cannot be driven, and hence the vehicle cannot be run.
The second prior art device can drive the vehicle even if one power converter fails, as it has the same number of power converters as it has motors. However, the requirement for multiple motors complicates the drive system for the electric vehicle.
The third and fourth prior art devices provide a plurality of power converters. However, these patent documents do not consider which one or how many power converters are used for driving.
In view of the foregoing, a first object of the present invention is to provide a simple electric vehicle control system, for optimal control of a plurality of power converters, depending on the drive state of the electric vehicle.
A second object of the present invention is to provide an electric vehicle that can run safely, even if any one of the power converters fails.
A third object of the present invention is to provide an electric vehicle control which is efficient and highly reliable, with a longer service life.